Conventional therapies for cancer as radiotherapy and chemotherapy are characterized by poor survival rates in many forms of cancer. This is due to multiple factors including the development of drug-resistant tumor cells and the presence of undetectable micrometastases at the time of diagnosis and treatment. The other substantial limitation of conventional cancer chemotherapy and radiotherapy is the toxicity of these agents to normal tissue. A major challenge in treating cancer is the difficulty of bringing therapy to poorly perfused areas of solid tumors, which are often most resistant to chemo- and radiotherapy. This has prompted the development of many new approaches for the treatment of cancer, including the delivery of anti-cancer genes to the tumor site in various gene therapy protocols. These genetic approaches include delivering genes encoding pro-drug activating enzymes, cytotoxic, antiangiogenic proteins or cell-targeted toxins to the tumors. However, current gene therapy strategies require local administration of vectors, which limits their usefulness. Hence, there is a need in the art for an effective and largely non-toxic therapy to fight tumor growth and metastasis.